Xylitol is a naturally occurring five carbon sugar alcohol. It occurs naturally in many fruits and vegetables and is produced by the human body during normal metabolism. It is a sweet crystalline product, white in color, odorless and soluble in water. In crystalline form, it quickly dissolves in the mouth. It has a negative heat of dissolution, and thereby produces an agreeable refreshing or cooling effect in the mouth.
In addition to its cooling effect, xylitol has interesting sweetening qualities. If one takes sucrose as a reference point, and attributes to it a sweetening value of 1, xylitol is found to have a sweetness of the same order. Thus, xylitol is a sugar substitute. In fact, it has the same sweetness and bulk as sucrose with one third fewer calories (2.4 calories per gram) and no unpleasant after taste. It is currently approved around the world for use in foods, pharmaceuticals and oral hygiene products. For example, xylitol has been widely used in confectionery, baking products, cereals, desserts, jams, beverages, chocolate, chewing gum, gumdrops, and ice cream to name just a few products. It has also been used in the production of oral hygiene products, such as toothpaste and in pharmaceutical products. In addition, it is used as a sucrose substitute placed in foods for consumption by people with diabetes.
Further, xylitol has an interesting property for dental health, in which it differs from other known polyols. It is, in fact, anti-cariogenic, i.e., it cannot serve as a substrate for bacteria present in the mouth cavity. Moreover, it also plays a role in preventing dental caries. It inhibits the growth of Streptococcus Mutans, the primary bacteria associated with dental caries. Recent interest has increased in xylitol-containing candies because xylitol has been shown to promote remineralization of teeth and damaged tooth enamel. It has also been found that regular use of xylitol can inhibit the transfer of cariogenic Streptococcus Mutans bacteria from mothers to their newborn children. Studies have shown that mothers are the primary source of infection of Streptococcus in the mouths of newborns and that prevention or delaying colonization by these bacteria leads to significant reduction in tooth decay later in life. In addition, xylitol reduces plaque accumulation and inhibits plaque regrowth.
Further, it also increases salivary flow. Saliva helps clean and protect teeth from decay and this plays a role in repairing the damage caused in the early state of the decay process.
Thus, it is important to have a method of producing products comprising xylitol for use in these various applications.
One such product is a hard candy comprised of xylitol. However, producing a hard candy of xylitol is challenging. It is difficult for xylitol to be made into a hard candy free of crystals because its glass transition is below 32 F (0 C) and at normal household conditions, it would exist as a liquid, although because of its instability, would slowly transform to a few large crystals grown loosely together. Furthermore, as a crystal, it does not compact well.
In addition, in preparing hard candies comprising xylitol, the xylitol is traditionally melted completely to form a molten mass. The molten mass is mechanically agitated or seeded with xylitol crystals to cause crystallization. The resultant seeded mass is then combined in a layered format, wherein an isomalt base is first deposited, then followed by a xylitol layer or the xylitol is codeposited with isomalt in a mold to produce hard candy.
The problem often encountered in this process is that the final product is usually hygroscopic and sticky. Further, the molten mass often manages to crystallize in the machinery and/or equipment, thereby clogging the machinery and/or equipment. Further, once the seed crystals have been added, the viscosity of the seeded molten mass is very difficult to control. Moreover, the product is very temperature sensitive. The seeded mass thickens and crystallizes rapidly if the temperature falls below the melting point of xylitol, and on the other hand, thins, due to melting of the seed crystals if the temperature is raised above the melting point. As a consequence, the viscosity and density of the seeded mass tends to vary upon prolonged exposure to a molten state which is particularly undesirable in deposited hard candy manufacturing lines where any inconsistency of the seeded mass leads to inconsistent piece weight and potential equipment failure. Further, the resultant candy is quite hard, and difficult to bite through.
The present inventors were investigating a new method for producing a hard candy comprising xylitol by modifying the methodology of the prior art. They began preparing the hard candy in a scraped surface heat exchanger, maintaining the temperature at or above the melting point of xylitol. Even though they initially worked with a complete melt, when they lowered the temperature in the scraped surface heat exchanger below the melting point of xylitol, crystals of xylitol began to form in the scraped surface heat exchanger and begin to clog the machine. Once the xylitol recrystallized, it became extremely difficult to work with. The inventors also noted that the product was hard and was not easily bitten into. Moreover, the inventors have confirmed that if the temperature of the emitted scraped surface heat exchanger was too hot, such material was difficult to handle and the product obtained was undesirable.
However, the inventors found that if the xylitol was not completely melted in an extruder, the resulting product was different and was much softer than the product comprising xylitol obtained from completely melting the solid and recrystallizing the melted solid in a scraped surface heat exchanger. Further, in the method found by the present inventors, since the xylitol solid was not being recrystallized, the extruder was no longer getting clogged.
The present invention thus describes this process which overcomes the problems enumerated above and provides a product which has a high flavor impact and a strong cooling sensation. Yet, at the same time, the product that is produced is a soft product that can be easily bitten through.